This application is the U.S. national phase of International Application No. PCT/FI2009/050494 filed 10 Jun. 2009 which designated the U.S. and claims priority to FI Patent Application No. 20080403 filed 11 Jun. 2008, the entire contents of each of which are hereby incorporated by reference.
The present invention relates to an apparatus for storing rolling material in an open storage pile and more specifically to an apparatus for stacking and reclaiming material, i.e. to a stacker/reclaimer. Most preferably the invention relates to storing of wood chips, but it is applicable for storing other granular material such as wood bark, coal, corn or fine-grained material.
Storage piles are needed for homogenizing the material and on the other hand for blending possibilities. The stacker/reclaimer for this kind of storage pile comprises two main parts: the stacking system and the reclaiming system. The stacker/reclaimer comprises e.g. a center column, a stacker conveyor and a reclaimer conveyor. The center column supports concentrically the upper stacker conveyor and the lower reclaimer conveyor. The stacker conveyor adds loose material in the pile, while the reclaimer conveyor conveys the material from the pile towards the slewing center of the stacker/reclaimer. In the slewing center the material to be discharged is transferred to an underground discharge conveyor. Both the stacker and the reclaimer are independently turnable around the center column; first the stacker forms an arched pile around the center column and the reclaimer follows discharging material from the first-built part of the pile. Thus the stacker/reclaimer achieves a real FIFO (FirstInFirstOut)-operation.
In many prior art stacker/reclaimers the stacker boom is supported on a slewing bearing with a diameter up to 2.5 meters and located at the end of the center column. In some known solutions the slewing bearing is close to the ground level. A slewing bearing is expensive and its delivery time from purchase order is long, even up to approximately 2 years. If the slewing bearing gets damaged, its replacement is very labor-consuming and expensive. The stacker boom is supported at one point directly on concrete supports arranged in the center column. Additionally, the concrete construction of the center column extends up to the slewing hinge. Rotating power supply to the booms has traditionally been arranged on the outer surface of the center column due to the concrete construction of the column. This kind of center column construction is heavy and expensive to build.
A further problem of prior art is difficult controlling of the so-called emergency slewing. In prior art technique, when emergency slewing is required, i.e. when the wind is heavy, the brake of the electric motor of the boom-slewing device is opened. However, this kind of solution involves the risk damage of the electric motor or the slewing gear due to uncontrollable slewing speed. If said parts when damaged jam during heavy wind, rapid stopping can harm the slewing bearing, or the stacker pile or the center column can be damaged e.g. by twisting or rotating.